1. Field of the Invention
The present invention relates to a mirror driving device for use in a single lens reflex camera, and is particularly directed to such a mirror driving device as will not damage the other components even if a mirror is carelessly moved when the mirror is in a viewing-focusing position.
2. Description of the Prior Art
According to the prior art, in a single lens reflex camera, a similar device is already provided in which a pin movable integrally with the mirror is pinched between a lever and a spring and wherein the mirror may be retracted from the viewing position to a position outside an optical path during phototaking by moving said lever and be then returned to the viewing position in the optical path by the biasing force of said spring as the lever returns to its original position. In this viewing position the mirror is positioned by said biasing force of the spring.
In such a prior art device, however, the stronger the force of the spring becomes, the bigger the friction between the spring and the pin gets when the mirror ascends to make it difficult for the mirror to be instantaneously raised, while a spring having weak biasing force will result in delayed descending operation of the mirror at returning movement of the lever. Consequently such a known device is disadvantageous in that high-speed motion of the mirror is prevented whether the spring force is selected strong or weak.